A caveat is a serious matter, and it is a great shame your lawyer lawyer has been this non-responsive, but then again he was recommended by the agent which is a sign.
Property buyers certainly should do diligent homework as to who they are working with and how careful they are of their profession and practice, and only work through references that you know can cause the lawyer an immediate loss of a whole chain of business if negligence occurs.
Anyway, you need to settle and remove the caveat. Try the bank first, if it is a silly matter and they are not being reasonable, I hear there are ways to remove the caveat directly at the land department. But if there is proof of remaining funds that have not being settled and all that then it'll stay until you sort it.
Good luck.